Motor vehicle with electrical generator

ABSTRACT

A motor vehicle with a combustion engine ( 2 ), a transmission ( 8 ) and a mechanical drive line ( 6 ) comprises a coaxially disposed electric generator ( 10 ) for providing power to electric loads, said generator being coupled directly with the crankshaft ( 4 ) of the combustion engine. The rotor of the generator serves as a flywheel in particular when the generator is designed in outside rotor construction. Stator and rotor of the generator are each formed as hollow cylinders and have a small axial length in comparison to the mounting diameter of the generator. The generator can also be used as a starter motor when operated as a motor. An additional possibility of application is for damping the torsional vibration of the crankshaft of the combustion engine, the transmission and the mechanical drive line.

BACKGROUND OF THE INVENTION

The invention relates to a motor vehicle comprising a combustion engine,a mechanical drive line coupled with the shaft of the combustion engine,and an electric generator driven by the combustion engine.

The present invention concerns specifically the formation andarrangement of the electric generator. In conventional motor vehicles,the generator is driven by the output shaft of the combustion engine viaa V-belt. The electric power demand has increased greatly in recentyears not only for road vehicles, but also for motor trucks, buses andthe like, so that the electric generator (alternator) has been madeincreasingly efficient. If necessary, a plurality of electric generatorshas been provided.

The usual board wiring voltages (12 V/24 V), in case of high-powerelectric loads, necessitate correspondingly high currents. Thecross-sectional areas of lines must be selected correspondingly large.

SUMMARY OF THE INVENTION

It is the object of the invention to make available a motor vehicle ofthe type indicated hereinbefore, in which relatively high electric powercan be supplied by the electric generator despite a compactconstruction.

This object is met according to the invention in that the generator isdisposed with is rotor coaxial to the shaft of the combustion enginebetween the latter and the input of the drive line, and is drivendirectly by the shaft, and in that the electric output of the generatoris connected to a power electronics unit.

It is preferred to equip the rotor with (high-energy) permanent magnets.Rotor and stator of the generator are advantageously disposed spatiallybetween the combustion engine and the drive line and form a modular unitwhich can be mounted quickly and without a problem.

Due to the fact that there is no intermediate mechanical connectionbetween combustion engine and generator, i.e. in particular as the beltdrive in conventional vehicles is omitted, a compact construction isobtained. The drive line is coupled directly to the electric generatorand contains on the input side e.g. an automatic transmission with atorque converter or a shift transmission with a clutch.

With conventional engines there is enough space available in the area ofthe output shaft of the engine to accommodate the electric generatorthat is preferably formed as a thin disk. Due, to the permanent-magneticexcitation, one can make good use of the structural space available forthe generator, thereby achieving high torque and thus high electricpower in relation to the volume and weight of the generator. Theelectric power of the generator is preferably in the range between 5 and10 kW. The generator can thus easily provide the power to be deliveredin conventional vehicles. However, a generator with the describedarrangement and construction can also easily realize far higher powers(>50 kW) which are needed for example in heavy vehicles when secondaryor additional loads normally driven mechanically are advantageouslychanged to electric drive (e.g. steering booster pumps, air-conditioningor cooling units and the like).

For being able to design the generator in compact manner as a module,the diameter is selected relatively large while the axial length isrelatively small.

It is possible to give the generator a so-called inside rotorconstruction, in which the rotor rotating with the crankshaft of thecombustion engine is on the inside while the stator is disposed radiallyoutside the rotor.

However, the so-called outside rotor construction has certainadvantages. When the rotor is outside and the stator inside with thisoutside rotor construction, one can utilize the then especially highmass moment of inertia of the rotor, so that no additional flywheel isrequired in addition to the rotor. This holds equally for the insiderotor design with a correspondingly high mass moment of inertia of therotor.

The design of the generator with a rotor and a stator each formed as athin-walled cylinder leaves enough space in the area of the axis of theengine shaft to permit parts of the transmission or clutch to bereceived therein. This permits the overall constructional length ofcombustion engine/generator/transmission to be kept very short. Aparticularly favorable ratio of mounting diameter to mounting length ofthe generator has turned out to be a value of 2 or more. That is to say,the diameter of the generator is at least twice as large as the axiallength thereof.

The rotor can take over a further function of the fly-wheel by beingequipped with external teeth meshing with the pinion of the startermotor. This possibility can be realized especially easily with theoutside rotor construction, but is also possible with an inside rotor ifthe stator is mounted suitably.

The torque to be applied for starting the combustion engine need not beapplied solely by the electric starter motor; the generator itself canoperate as a motor to support the separate starter motor or even replaceit completely for starting the combustion engine. The generator is thenfed by the on-board battery via the afore-mentioned power electronicsunit, so that the torque supplied by the generator operating as a motorsupports the starter motor. With an especially strong generator, thetorque thereof might possibly suffice alone for starting the combustionengine, so that a separate starter can be dispensed with. A specialmeasure of the invention provides for the use of a separate electronicassembly for the motor mode of operation. This permits both thegenerator and the motor mode of operation to be represented withassemblies designed for each particular case.

The modular generator is expediently provided with input-side andoutput-side standard flanges so that it can be coupled with the engineblock and gearbox, respectively, without requiring any specialadaptation measures. The generator can be manufactured in differentoverall sizes/power outputs and is provided with standard flanges.

The power electronics unit serves as a commutating means which firstconverts the alternating voltage delivered by the generator into adirect voltage and forms a direct-voltage intermediate circuit. Thevoltage in the direct-voltage intermediate circuit is preferably between100 and 1000 volts. With this direct voltage, separate electronicassemblies can produce different direct voltages and alternatingvoltages with the suitable frequency and amplitudes for special loads.However, the direct voltage of the intermediate circuit can also be useddirectly for providing power to corresponding loads.

Another possibility consists in giving the power electronics unit e.g. adirect converter design so that it supplies the voltages and frequenciesrequired by the various loads directly at its output terminals.

Due to the relatively high voltage in the direct-voltage intermediatecircuit, it is possible to feed certain loads with relatively highvoltage, for example heating elements which require a relatively highamount of power. The relatively high voltage permits the use of lineswith comparatively small line cross-sectional area. In addition, it isfavorable for the dimensioning of semiconductor switches.

It is expedient to provide the power electronics unit with an automaticcontrol system for controlling and regulating the loads connected on theoutput side with respect to the electrical power drawn by them. This ispreferably done according to preset values to be achieved by the loads(for example the temperature of the cooling unit). This system can bepart of the power electronics unit itself or be provided as separatecontrol acting on individual loads or load groups.

An independently protected measure of the invention consists in that theautomatic control system of the power electronics unit serves to controlthe operation of the combustion engine.

When a certain power is taken up from the engine by the drive line fordriving the vehicle, the power electronics unit can control the enginein such a way that the mechanical power required for an electricaloutput power delivered by the generator is made available by thecombustion engine without diminishing the power supplied by thecombustion engine to the drive line. The above-described control system,however, can also serve very special purposes; for example, the powerelectronics unit can adjust the output for certain or all loads downwardoptionally to zero or a minimum, when the entire or almost the entirepower of the combustion engine is to go to the drive line. This may bethe case e.g. when maximum vehicle acceleration is desired.

It was mentioned hereinbefore that the generator can be used as a motor,so that the motor can be used for example for starting the combustionengine. In general it is of course also possible to use the motor fordriving the drive line if suitable electric power and energy arepresent. For this purpose the power electronics unit then contains, in amanner known per se, four-quadrant inverse rectifiers in the form ofseparate assemblies. When the generator operates as a motor, theelectric current is then fed via these assemblies.

Another generator application claimed by the invention is for damping oreliminating disturbances in the uniform speed pattern of the crankshaftof the combustion engine and the drive line, which lead to undesirablenoise being caused in the vehicle. In the simplest case, these may alsobe torsional vibrations of the parts mentioned.

The afore-mentioned damping effect is achieved in that, upon changes inthe actual rotor speed with respect to the average rotor speed, torquesand thus forces counteracting these changes in direction and amplitudeare applied to the rotor via the stator. This is done by correspondinglyincreasing or decreasing the current in the stator coils which iscontrolled by the associated power electronics unit.

In other words, if there is e.g. a brief positive acceleration of therotor, a braking force is applied by the stator by means ofcorresponding current variation in the power electronics unit. In thenormal generator mode of operation of the generator, this means a briefincrease in coil current as compared to the normal operating value, sothat more power, i.e. torque is taken off and the excessive speed isdecelerated.

However, if the rotor is decelerated in relation to the uniform speede.g. by a torsional vibration, the torque taken off from the generatoris reduced by the stator through current reduction—again considering thegenerator mode of operation of the generator—, resulting in a positivelyaccelerating force being exerted on the rotor.

Both modes of operation, i.e. active torque increase and decrease on thegenerator rotor, follow one after the other since every completetorsional vibration means an acceleration and deceleration of the rotor,or vice versa. The actively applied antitorque moment follows therotational acceleration with a certain phase shift, resulting altogetherin only a torsional vibration with a greatly reduced amplitude, i.e. adamped torsional vibration. Conceivable is also an adaptivestabilization by determining the vibration pattern of the torsionalvibration as a characteristic feature of the overall arrangement ofcombustion engine and generator, and performing an opposite adjustmentin phase and amplitude, so that the vibrational excitation is reduced tozero. This can be done by a so called fuzzy control.

For detecting the changes in rotor speed, one can use a positionindicator system in the generator from the signals of which the speed ofthe rotor is determined. The stated torsional vibrations then manifestthemselves as pulsations in the speed with respect to the averaged speedvalue which can be filtered out accordingly.

It is preferred to use for the purpose mentioned the power electronicsunit connected to the generator and serving for decoupling the electricpower. Thus, no additional parts are necessary, in particular becausethe torsional vibrations, apart from the losses related thereto, meanonly energy fluctuations. Depending on the special properties of thecombustion engine and its rotating parts, the stated speed pulsations orvibrations, however, can also be of particularly high frequency, i.e.far above the normal operating speed of the rotor. In such cases it isparticularly preferred to install an additional, especially fast-workingpower electronics and control assembly separately from the electronicsunit serving to couple out electric power.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, embodiments of the invention will be elucidated inmore detail with reference to the drawings, in which

FIG. 1 shows a schematic view of the drive part of a motor vehicle,

FIG. 2 shows a schematic sectional view of the electric generator shownin simplified form in FIG. 1, along with the associated powerelectronics unit,

FIG. 3 shows a schematic view of a modified embodiment of an electricgenerator,

FIG. 4 shows a schematic view of a further modified embodiment of anelectric generator,

FIG. 5 shows a schematic circuit diagram of the power electronics unitwhich contains separate electronic assemblies (inverse rectifiers) ofthe direct-voltage intermediate circuit and control means for theelectronic ignition, and

FIG. 6 shows a longitudinal sectional view through a practicalembodiment of an electric generator disposed in the flywheel housing ofa combustion engine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows schematically a combustion engine 2, with the indicatedpistons rotating via connecting rods a crankshaft 4 whose output at theright-hand end of the engine 2 extends through the housing of anelectric generator 10. The drive line 6 starting out from crankshaft 4contains a transmission unit 8 including a torque converter or a clutch.

As shown schematically in FIG. 1, electric generator 10 is located atthe level of crankshaft 4 of engine 2 so that the rotor of generator 10is in concentric arrangement with crankshaft 4 and rotates together withcrankshaft 4.

As regards the construction, the housing of generator 10 consists of athin disk whose axial length is smaller than its diameter; in theexample shown the diameter is about twice as large as the axial lengthof generator 10. FIG. 2 indicates the diameter D and the axial length x.The ratio D/x is ≧2. As can be seen in FIG. 2 furthermore, generator 10is accommodated in a housing 20 which can be threadedly mounted to theblock of combustion engine 2 and to the input side of transmission 8,respectively.

In FIG. 2 the engine is disposed on the left-hand side, and the driveline 6 inclusive of transmission 8 on the right-hand side.

Electric generator 10 contains a stator 22 formed as a thin-walledcylinder connected to housing 20 in a manner not depicted in moredetail.

Rotor 24 that is likewise formed as a thin-walled cylinder is coupledwith crankshaft 4 of combustion engine 2. A disk-shaped or bell-shapedcarrier branches off from crankshaft 4 in radial direction, havingmounted on the peripheral area thereof high-energy permanent magnetsspaced only a small distance from the outer circumferential surface ofstator 22.

Rotor 24 constitutes a mass moment of inertia so that the rotor alsofunctions as a flywheel for combustion engine 2.

Extending from stator 22 are connecting cables 26 to a power electronicsunit 12 formed in a manner known per se, i.e. containing adirect-voltage intermediate circuit delivering a direct voltage of U1100 V in the present case. Following the direct-voltage intermediatecircuit is an inverse rectifier assembly, which in the embodiment shownin FIG. 5 is in the form of separate electronic assemblies combined inan assembly unit 13 for converting voltage for individual loads or loadgroups.

According to FIG. 5, a section 13 a and a section 13 b supply twodifferent voltages U1 and U2, which may be different direct voltages. Asection 13 c supplies an alternating voltage U3 having a frequency f. Anassembly 13 d supplies an additional alternating voltage U4 having adifferent frequency f′. An additional inverse rectifier 13 m suppliesthe drive current for the generator when the latter is operated as amotor.

The construction of rotor 24 and stator 22 in the form of a thin hollowcylinder each, as outlined in FIG. 2, still leaves considerable space inthe area of crankshaft 4, in which a part of the drive line, in theinstant case of transmission 8, can be installed. This end portion oftransmission 8 facing the engine with crankshaft 4 protrudes into theinterior of stator 22. By exploiting this space, one can shorten thetotal length of combustion engine 2, electric generator 10 andtransmission unit 8.

Power electronics unit 12 additionally contains a control means 12A forthe combustion engine, i.e. for the electric/electronic injection systemof the combustion engine. The control means 12A contained in powerelectronics unit 12 can be used to control the power of the combustionengine so that it also provides the power for generator 10 in additionto the mechanical power to be supplied via the drive line.

A specific feature of power electronics unit 12 or assembly unit 13,respectively, is that all connected electric loads are switched off orswitched to economical operation in certain situations so that thecombustion engine is able to give almost its entire power to the driveline, as is necessary e.g. in case of maximum acceleration.

Due to the fact that different direct voltages and alternating voltageswith different frequencies are provided individually, individual loadscan be supplied with electric power separately. For example, assemblyunit 13 can supply via its section 13 a a relatively high direct voltageof 100 V to powerful loads, for example heating elements. The relativelyhigh voltage permits a reduction of the cross-sectional areas of thelines and also a favorable dimensioning of semiconductor switchesassociated with the individual electric loads.

FIG. 3 shows a modified embodiment. In this embodiment, the rotor isformed as an inside rotor while the stator is located radially outsidewith respect to the inside rotor.

In case of the variant shown in FIG. 4, the rotor is formed as anoutside rotor and has on its outside teeth means, not shown in moredetail in the drawing, meshing with a pinion 30 of an electric startermotor 32 for starting combustion engine 2. The generator operating as amotor can then be used in conjunction with starter motor 32 for startingcombustion engine 2.

The electric generator provided according to the invention, in a mannerknown per se, feeds the entire board wiring system, but can furthermorealso be used for operating additional devices or external devices, forexample for operating pump motors, fan drives and the like. As pointedout hereinbefore, starter motor 32 according to FIG. 4 serves to startthe combustion engine in conjunction with the generator which thenoperates as a motor. However, one can also use solely the separatestarter motor for starting the engine.

FIG. 6 shows a longitudinal sectional view through an electric generator10 disposed between combustion engine 2 and transmission 8 in a specificconstruction. Transmission 8 ends with a transmission cover 42 whoseperipheral flange in conventional vehicles is threadedly attached to thematching standard flange of the engine block, but which according toFIG. 6 is attached to the outside flange of the generator housing, theoutside flange being in turn connected to the corresponding flange ofthe flywheel housing of combustion engine 2.

Via a connecting piece 40, the electric connecting cables 26 shownschematically in FIG. 2 are fed to the engine. Connecting piece 40contains furthermore coolant tubes. Both the coolant tubes and theconnecting cables, which are not shown specifically in FIG. 6, areguided in integrated channels within transmission cover 42. The inputshaft of the transmission is coupled with crankshaft 4 via a plug-typetooth means. A flexible coupling 46 can be disposed between generatorand transmission 8.

A high-resolution position indicator system 47 a, 47 b is used to detectthe position of rotor 24 relative to stator 22 in the course ofrotation. This can be realized for example by superimposing twoalternating field signals which are evaluated in a suitable electronicsunit. The rotor speed can be calculated from the change in the rotorposition signal, and deviations of the momentary rotor speed from theaverage value or between actual value and desired value can be detectedby averaging or by comparison of actual speed value and desired speedvalue. The reaction of the generator and the power electronics unitconsists in applying positive or negative additional forces duringrotation which counteract the negative or positive speed deviations,respectively, or, in other words, the forces causing these deviations.

What is claimed is:
 1. An electrical generator system for a motorvehicle, comprising: (a) a combustion engine having a shaft; (b) amechanical drive train coupled with the shaft; (c) an electric generatorhaving a rotor, a stator, and an electrical output, disposed with itsrotor coaxial to the shaft of the combustion engine and positionedbetween the engine and the input of the drive train, and driven directlyby the shaft; and (d) a power electronics unit having an input connectedto the electrical output of the generator, wherein (e) the powerelectronics unit is connected to the combustion engine and is responsiveto a change in the electrical output of the generator to control thecombustion engine to perform a corresponding change in the enginemechanical power output, and (f) the power electronics unit furtherincludes a direct-voltage intermediate circuit having a voltage of atleast 100 V, the direct-voltage intermediate circuit supplying power toat least one of (1) electrical loads connected directly to thedirect-voltage intermediate circuit and (2) electrical assemblies thatproduce different voltages for electrical loads .
 2. The system of claim1, wherein the rotor and the stator of the generator are disposedspatially between the combustion engine and the transmission.
 3. Thesystem of claim 1, wherein the generator comprises outside rotorconstruction with the rotor outside and the stator inside.
 4. The systemof claim 1, wherein the generator comprises inside rotor constructionwith the rotor inside and the stator outside.
 5. The system of claim 1,wherein the rotor includes permnanent-magnetic excitation.
 6. The systemof claim 1, wherein the rotor and stator of generator each comprisethin-walled cylinders and a part of the mechanical drive line isreceived for coupling with the shaft in the space located radiallyinside with respect to the stator and the rotor.
 7. The system of claim1, wherein the generator has a mounting diameter and an axial mountinglength, and the ratio of mounting diameter to axial mounting length is≧2.
 8. The system of claim 1, wherein the rotor of the generatorcomprises a flywheel of the combustion engine.
 9. The system of claim 1,wherein the rotor of the generator includes external teeth means meshingwith a starter pinion.
 10. The system of claim 1, wherein the housing ofthe generator includes mounting flanges corresponding to the standarddimensions of flanges of combustion engines.
 11. The system of claim 1,wherein the direct-voltage intermediate circuit delivers a directvoltage between 100 and 1000 V.
 12. The system of claim 1, wherein theoutput of the power electronics unit produces voltages and frequenciesfor the loads directly on the output side.
 13. The system of claim 1,wherein the power electronics unit further includes anelectric/electronic power control for selectively controlling the loadsconnected.
 14. The system of claim 1, further including a separate powercontrol for individual loads or load groups.
 15. The system of claim 1,wherein the electric generator supplies power to at least one of a boardwiring system of the vehicle and additional external electric equipment.16. The system of claim 1, wherein the generator is operable as a motorand serves as one of a starter for the combustion engine and a supportfor a separate starter motor.
 17. The system of claim 1, wherein thepower electronics unit has a generator mode to perform power electronicscommutation and a motor mode to control the generator when operated as amotor.
 18. The system of claim 1, wherein the power electronics unitfurther includes an electronic assembly for a motor mode of operation ofthe generator.
 19. An electrical generator system for a motor vehiclecomprising: (a) a combustion engine having a shaft; (b) a mechanicaldrive train coupled with the shaft; (c) an electric generator having arotor, a stator, and a electrical output, disposed with its rotorcoaxial to the shaft of the combustion engine between the engine and theinput of the drive train, and driven directly by the shaft; and (d) apower electronics unit having an input connected to the electricaloutput of the generator, wherein (e) the power electronics unit isconnected to the combustion engine and is responsive to a change in theelectrical output of the generator to control the combustion enegine toperform a corresponding change in the engine mechanical power output,and (f) the power electronics unit further includes outputs for directlysupplying at least one of (1) different voltages and (2) differentfrequencies for electrical loads.
 20. The system of claim 19, whereinthe generator comprises outside rotor construction with the rotoroutside and the stator inside.
 21. The system of claim 19, wherein thegenerator comprises inside rotor construction with the rotor inside andthe stator outside.
 22. The system of claim 19, wherein the rotorincludes permanent-magnetic excitation.
 23. The system of claim 19,wherein the rotor and stator of the generator each comprise thin-walledcylinders and a part of the mechanical drive line is received forcoupling with the shaft in the place located radially inside withrespect to the stator and the rotor .
 24. The system of claim 19,wherein the generator has a mounting diameter and an axial mountinglength, and the ratio of mounting diameter to axial mounting length is≧2.
 25. The system of claim 19, wherein the rotor of the generatorcomprises a flywheel of the combustion engine.
 26. The system of claim19, wherein the rotr of the generator includes external teeth meansmeshing with a starter pinion.
 27. The system of claim 19, wherein thehousing of the generator includes mounting flanges corresponding to thestandard dimensions of flanges of combustion engines.
 28. The system ofclaim 19, wherein the power electronics unit further includes adirect-voltage intermediate circuit delivering a direct voltage between100 and 1000 V.
 29. The system of claim 28, wherein the direct-currentintermediate circuit has at least one of electronic loads directlyconnected directly to the circuit and electronic assemblies connected tothe circuit for converting voltage of different voltages.
 30. The systemof claim 19, wherein the power electronics unit further includes anelectric/electronic power control for selectivelycontrolling the loadsconnected.
 31. The system of claim 19, further including a separatepower control for individual loads or load groups.
 32. The system ofclaim 19, wherein the electric generator supplies power to at least oneof a board wiring system of the vehicle and additional external electricequipment.
 33. The system of claim 19, wherein the generator is operableas a motor and serves as one of a starter for the combustion engine anda support for a separate starter motor.
 34. The system of claim 19,wherein the power electronics unit has a generator mode to perform powerelectronics commutation and a motor mode to control the generator whenoperated as a motor.
 35. The system of claim 19, wherein the powerelectronics unit further includes an electronic assembly for a motormode of operation of the generator.
 36. The system of claim 19, whereinthe rotor and the stator of the generator are disposed spatially betweenthe combustion engine and the transmission.